Chris,
The Signalink works differently than other interfaces in that it uses VOX for PTT. You also can not
pull audio over the serial port (or any serial port, for that matter). If you mean the USB port, then
the answer is also no, the RRC does not provide audio that way.
The best way to do this is to plug the Signalink into the RJ45 MIC/AUX jack of the control RRC. If it
is too much of a hassle to unplug the microphone, you can build a Y-cable. You can pull the audio off
of the control RRC's SP jack and maintain a constant audio that way and still be able to hear over the
TS-480 head.
CAT control is pulled off of COM2. Let me know if you need my TS-480 CAT checklist for that.
73,
Mitch DJ0QN / K7DX